1. Field of the Invention
The present invention relates to an inkjet recording apparatus and an image forming method, and more particularly, to an image forming technology using ultraviolet-curable ink.
2. Description of the Related Art
Inkjet recording apparatuses having a structure which forms a desired image on a recording medium by ejecting color ink from an inkjet head have been known as a general image forming apparatus. In recent years, non-permeable (low-permeability) media such as a resin film have been used, in addition to media having permeability such as paper, and apparatuses which cure ink deposited on a medium by radiating ultraviolet light as active light have been proposed.
In an inkjet recording apparatus which uses ultraviolet-curable ink, a light source for radiating ultraviolet light is mounted on a carriage on which an inkjet head is installed, the ultraviolet light source is scanned (moved) so as to follow the inkjet head, and ultraviolet light is radiated onto ink droplets immediately after landing on a medium, thereby preventing positional displacement or dots interference of the ink droplets.
Furthermore, in order to improve the glossiness of a color image, a method is known in which a layer of clear ink (transparent ink) is formed on a color image. Various modifications are made in order that the cured state of the clear ink affects the glossiness of the image.
Japanese Patent Application Publication No. 2006-289722 discloses an inkjet recording apparatus which is composed so as to eject colored ink from a colored ink recording head, radiate light onto the colored ink by a light irradiation apparatus, and then eject transparent ink from a transparent ink recording head and radiate light from the light irradiation apparatus after a prescribed time period has elapsed. In the inkjet recording apparatus, by keeping a uniform time from the deposition of the transparent ink onto the recording medium until the irradiation of light, a uniform dot diameter is achieved regardless of the direction of movement of the transparent ink recording head, thereby preventing non-uniformity in glossiness.
Japanese Patent Application Publication No. 2010-149516 discloses an inkjet printer which is composed so as to print a color image by radiating ultraviolet light while ejecting color ink onto a recording medium, in a serial type image formation method, and to pull back the recording medium to the printing start position after printing of the color image, eject clear ink onto the recording medium on which the color image has been printed while the ultraviolet lamps are extinguished, and to then radiate ultraviolet light onto the clear ink that has been ejected onto the recording medium. This inkjet printer resolves a phenomenon of loss of glossiness by preventing the clear ink deposited on the recording medium from curing before the ink becomes flat.
Japanese Patent Application Publication No. 2009-51095 discloses an inkjet recording apparatus which is composed so as to enable variation in the glossiness of an image, by altering the intensity of ultraviolet light which is used to cure ink that has been deposited on the recording medium.
However, the inkjet recording apparatus disclosed in Japanese Patent Application Publication No. 2006-289722 discloses adjusting the time until ultraviolet light is radiated after deposition of clear ink onto a recording medium, but does not disclose the specific conditions of irradiation of ultraviolet light.
Furthermore, Japanese Patent Application Publication No. 2010-149516 and Japanese Patent Application Publication No. 2009-51095 disclose changing the glossiness of an image by altering the irradiation conditions of ultraviolet light, but do not disclose the specific conditions of irradiation of ultraviolet light.